1. Field of the Invention
This invention relates to a method for removing metal ions present in small amounts in aqueous solutions by means of a novel metal sequestering agent having a strong binding force with metal ions, especially with ions of heavy metals.
2. Summary of the Prior Art
Waste water emanating directly from metal ore mines, or mingled in neighboring streams, as well as waste water from industrial plants, especially from chemical plants, often contain a variey of dissolved metal ions, of which ions of heavy metals are especially known to be detrimental to humans and animals. Thus, removal of such ions from waste water before its discharge into a river, lake, or sewer can be desirable or even required by government regulation. It is known in the art to eliminate metal ions in contaminated waste water from mines or plants by treatment with a metal sequestering agent such as a condensed phosphate or ethylenediaminetetracetates which have the capacity to bind metal ions to form an inert complex compound in which the harmful action inherent in heavy metal ions is suppressed.
However, heretofore known metal sequestering agents such as condensed phosphates and ethylenediaminetetracetates are expensive because of the complexity of the process used for their production and hence are rarely used in large amounts for economical reasons. For the purification of contaminated waste water from mines and plants, the development of a new type metal sequestering agent which can be produced at a lower cost on an industrial scale and has a strong metal sequestering activity is a keenly felt need in the art.
Therefore, it is a prime object of this invention to provide a method for eliminating metal ions almost completely from solutions, especially aqueous solutions, containing a very slight amount of such metal ions.
It is another object of this invention to provide a new metal sequestering agent which is suitable for use in said method and can be prepared cheaply on an industrial scale.
These and other objects of this invention will become apparent as the description proceeds.